From f8f501ec9853231805097a5dbaf0ea99196e8014 Mon Sep 17 00:00:00 2001
From: "Bradley T. Hughes" <bradley.hughes@nokia.com>
Date: Fri, 9 Sep 2011 11:10:48 +0200
Subject: [PATCH] Make QLinkedListData::shared_null const

Similar to QList, QMap, QVector, QByteArray and QString, keep the
shared_null in shareable memory and never modify it.

Change-Id: I70b484d528c397a9d205b1418b6dc920c69dc725
Reviewed-on: http://codereview.qt-project.org/4532
Reviewed-by: Qt Sanity Bot <qt_sanity_bot@ovi.com>
Reviewed-by: Oswald Buddenhagen <oswald.buddenhagen@nokia.com>
---
 src/corelib/tools/qlinkedlist.cpp | 7 ++++---
 src/corelib/tools/qlinkedlist.h   | 8 ++++----
 2 files changed, 8 insertions(+), 7 deletions(-)

diff --git a/src/corelib/tools/qlinkedlist.cpp b/src/corelib/tools/qlinkedlist.cpp
index 97298dde3d..16105530bf 100644
--- a/src/corelib/tools/qlinkedlist.cpp
+++ b/src/corelib/tools/qlinkedlist.cpp
@@ -43,9 +43,10 @@
 
 QT_BEGIN_NAMESPACE
 
-QLinkedListData QLinkedListData::shared_null = {
-    &QLinkedListData::shared_null, &QLinkedListData::shared_null,
-    Q_BASIC_ATOMIC_INITIALIZER(1), 0, true
+const QLinkedListData QLinkedListData::shared_null = {
+    const_cast<QLinkedListData *>(&QLinkedListData::shared_null),
+    const_cast<QLinkedListData *>(&QLinkedListData::shared_null),
+    Q_REFCOUNT_INITIALIZER(-1), 0, true
 };
 
 /*! \class QLinkedList
diff --git a/src/corelib/tools/qlinkedlist.h b/src/corelib/tools/qlinkedlist.h
index 9f2834a7d7..bcad210d30 100644
--- a/src/corelib/tools/qlinkedlist.h
+++ b/src/corelib/tools/qlinkedlist.h
@@ -43,7 +43,7 @@
 #define QLINKEDLIST_H
 
 #include <QtCore/qiterator.h>
-#include <QtCore/qatomic.h>
+#include <QtCore/qrefcount.h>
 
 #ifndef QT_NO_STL
 #include <iterator>
@@ -59,11 +59,11 @@ QT_MODULE(Core)
 struct Q_CORE_EXPORT QLinkedListData
 {
     QLinkedListData *n, *p;
-    QBasicAtomicInt ref;
+    QtPrivate::RefCount ref;
     int size;
     uint sharable : 1;
 
-    static QLinkedListData shared_null;
+    static const QLinkedListData shared_null;
 };
 
 template <typename T>
@@ -81,7 +81,7 @@ class QLinkedList
     union { QLinkedListData *d; QLinkedListNode<T> *e; };
 
 public:
-    inline QLinkedList() : d(&QLinkedListData::shared_null) { d->ref.ref(); }
+    inline QLinkedList() : d(const_cast<QLinkedListData *>(&QLinkedListData::shared_null)) { }
     inline QLinkedList(const QLinkedList<T> &l) : d(l.d) { d->ref.ref(); if (!d->sharable) detach(); }
     ~QLinkedList();
     QLinkedList<T> &operator=(const QLinkedList<T> &);